Dietary Lipid Levels Research Articles

Performance, feed utilization, and hepatic metabolic response of weaned juvenile Atlantic bluefin tuna (Thunnus thynnus L.): effects of dietary lipid level and source

Two trials were performed using extruded diets as on-growing feeds for weaned Atlantic bluefin tuna (Thunnus thynnus; ABT) to establish adequate dietary levels of both lipid and omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs), and impacts on lipid metabolism via liver gene expression. In trial A, ABT were fed with either a commercial feed (Magokoro®; MGK) as a reference diet or two experimental feeds differing in lipid levels (15 or 20%) using krill oil (KO) as the single lipid source in order to estimate suitable lipid content. Fish fed MGK displayed the highest growth, followed by 15KO, and therefore a dietary lipid content of 15% was considered preferable to 20% at this stage. In trial B, fish were fed MGK, 15KO, or a feed containing 15% lipid with a blend of KO and rapeseed oil (RO) (1:1, v/v; 15KORO). Fish fed 15KO and 15KORO showed no difference in weight gain, specific growth rate, and fork length. Increasing dietary lipid level or including vegetable oil, RO, in the feeds did not increase liver lipid content. Liver fatty acid compositions largely reflected dietary profiles confirming very limited endogenous LC-PUFA biosynthesis. Liver of ABT fed 15KO and 20KO displayed the highest contents of docosahexaenoic acid (DHA). The hepatic expression of genes encoding enzymes and transcription factors involved in lipid and fatty acid metabolism, as well as genes encoding antioxidant enzymes, showed that many of these genes were regulated by dietary lipid and LC-PUFA content. Results suggested that ABT juveniles can be on-grown on inert dry feeds that support good fish growth and the accumulation of DHA.

Optimum level of dietary lipids for growth, chemical composition and apparent digestibility of lipids for Atractosteus tropicus

Lipids requirement of tropical gar Atractosteus tropicus prejuveniles and juveniles was evaluated on growth, survival, chemical composition and apparent digestibility coefficient (ADC). Four semi-purified experimental diets (5, 10, 15 and 20% of lipids) were obtained with a mix of menhaden oil and soybean lecithin (2:1 ratio). Two trials were carried out, first with 600 prejuveniles of 0.5 g (35 days post-hatching, dph) for 56 days, and the second with 160 juveniles of 15 g (two-months-old) for 42 days. In the first trial, 15 (40.8 g) and 20% (40.2 g) lipid diets showed the best weight. Significant differences were obtained in condition factor (CF), daily lipid intake (DLI), hepatosomatic index (HSI), crude protein, ashes, nitrogen-free extract, moisture and ether extract between treatments. In the second trial, fish fed with the 10% lipid diet obtained the highest weight (89.1 g) compared with the other treatments. Significant differences were recorded for weight gain (WG), feed conversion ratio (FCR), specific growth rate (SGR), condition factor (CF), and lipid efficiency rate (LER). Also, significant differences were obtained in crude protein, ether extract, NFE, gross energy, apparent lipid ADC, protein ADC and dry matter ADC. The polynomial models applied to both trials indicated an optimum lipid requirement of 17% for 0.5 g juveniles and of 9% for 15.2 g juveniles.

Effects of high-fat diets on growth performance, endoplasmic reticulum stress and mitochondrial damage in blunt snout breamMegalobrama amblycephala

This study aimed to investigate the relationship between fat deposition and endoplasmic reticulum stress of blunt snout bream through changing dietary lipid levels and adding lipolytic agents. The results showed that high fat diet (HFD) remarkably increased VSI, IPF, whole‐body lipid, tissue lipid contents, plasma levels of LDL‐C, TC and TG contents, cytosolic cytochrome c activity and Ca²⁺ content and the transcriptions of GRP78, IRE1, XBP1s and SREBP1, whereas the opposite was true for plasma HDL‐C content, SDH and Na⁺, K⁺‐ATPase activities in the mitochondria, Ca²⁺‐ATPase activity in the ER and the transcriptions of XBP1u, PPARα and CPT I. In addition, simvastatin supplementation remarkably decreased VSI, tissue lipid contents, plasma LDL‐C and TC levels, cytosolic cytochrome c activity and Ca²⁺ content and the transcriptions of GRP78, IRE1, XBP1s and SREBP1, while the opposite was true for plasma HDL‐C level, Ca²⁺‐ATPase activity and the transcriptions of XBP1u, PPARα and CPT I. Furthermore, the histological results showed that large lipid droplets and ultrastructural impairments of the mitochondria, nucleus and ER were present in hepatocytes of fish fed the HFD, while simvastatin supplementation had the potential to alleviate these damages. Taken together, these results indicated that there was an interaction between lipid deposition and endoplasmic reticulum stress induced by HFD.

Metformin attenuates lipid accumulation in hepatocytes of blunt snout bream (Megalobrama amblycephala) via activation of AMP-activated protein kinase

Currently, there is a trend to use high-fat diets in intensive aquaculture that is accompanied with incidence of fatty liver when dietary lipid level surpasses an upper limit. So, it is necessary to develop appropriate strategies to reduce the risk of fatty liver in commercial fish farming. Studies in mammals have revealed a correlation between fatty liver and AMP-activated protein kinase (AMPK) activity, which has been recognized as a key modulator of lipid metabolism. Considering the frequent occurrence of fatty liver in blunt snout bream farming, an in-vitro study was designed to evaluate the efficiency of metformin, as a stimulator of AMPK, in activation of AMPK and its subsequent effects on lipid metabolism in primary hepatocytes. Fish hepatocytes were seeded at a density of 1 × 106 ml−1 in 6-well tissue culture plates and treated with three different media including: 1) Leibovitz's L-15 medium [L15] as control, 2) high-fat medium [L15 + 400 μM oleic acid], and 3) metformin medium [L15 + 400 μM oleic acid+200 μM metformin]. After 48 h of culture, the cells and supernatant were collected for analysis. The results showed significant (P < .05) enhancement of cell triglyceride and total cholesterol concentrations in the high-fat group over control, and metformin addition significantly reduced the values. Also, the high-fat group exhibited significantly higher aspartate aminotransferase activity than both control and metformin groups. The lowest AMPK and phospho-AMPK protein expression was found in the high-fat group while metformin addition significantly up-regulated their expression levels. Mitochondrial and peroxisomal oxidation rates in the high-fat group were significantly lower than control while similar oxidation rates were observed for metformin treated and control groups. The high-fat group showed significantly lower CPT I activity than control, and metformin inclusion increased the activity. Expression of genes associated with lipid metabolism such as PPARα, CPT I, AOX, PGC-1α and TFAM was suppressed in the high-fat group, and metformin supplementation up-regulated their expression levels. The opposite trend was true for the expression of ACC2 gene. Also, the results showed down-regulation of FAS and SREBP-1C genes in the high-fat medium group, and metformin addition resulted in further reduction of their expression level. The lowest activities of mitochondrial complexes (I-III) were found in the high-fat group and metformin prevented high-fat-induced reduction of mitochondrial complexes activity. Notably increased concentrations of reactive oxygen species and malondialdehyde were found in the high-fat group, and metformin treatment reduced their concentrations. Moreover, metformin group exhibited higher glutathione peroxidase activity than the high-fat group. The findings in this study showed clearly that metformin activated AMPK in blunt snout bream hepatocytes, which contributed to enhanced lipid metabolism and attenuated lipid deposition in the cells incubated with high-fat medium.

Dietary lipid and carbohydrate interactions: implications on growth performance, feed utilization and non-specific immunity in hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂)

The present study was conducted to explore the effects of dietary lipid, carbohydrate and their interactions on growth performance, feed utilization, body composition and non-specific immunity of hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂). Nine isoproteic diets were formulated with three levels of dietary lipid (7, 10 and 13%) and carbohydrate (8, 12 and 16%) in a 3 × 3 factorial design. Triplicate groups of 30 juvenile fish (initial weight, 21.48 ± 0.24 g) were fed each of the diets twice daily to apparent satiation for 8 weeks. Results showed that a significant interaction between dietary lipid and carbohydrate was observed in the specific growth rate (SGR), and the SGR of grouper was not affected by dietary lipid but decreased significantly with the increase of dietary carbohydrate. Thereinto, grouper fed the diet containing 10% lipid and 8% carbohydrate obtained the highest SGR. Higher dietary lipid or carbohydrate significantly decreased feed intake (FI), but significantly elevated feed efficiency ratio (FER) and protein efficiency ratio (PER). Additionally, the retention rate of protein (PRR) and lipid (LRR) were both significantly improved with increasing dietary lipid level, while LRR was significantly decreased as dietary carbohydrate content increased. Meanwhile, significant interactions between dietary carbohydrate and lipid occurred in feed utilization. The apparent digestibility coefficient (ADC) of starch was significantly reduced with the increase of dietary lipid or carbohydrate level, and the interaction was also significant. With grouper fed the diet with 8, 12 and 16% carbohydrate, the postprandial glucose content peaked at the 3, 6 and 12h time-points, respectively. The activity of serum lysozyme increased significantly with the increase of dietary lipid, but significantly decreased as dietary carbohydrate content increased, while it was not significantly affected by the interaction. In addition, grouper fed the diets with 10% lipid obtained the highest SOD activity, in which no significant difference was observed with the increase of dietary carbohydrate content. In above, a combination of 10% lipid and 8% carbohydrate in the diet for this grouper should be optimum.

Feeding de-oiled rice bran based diet with varying level of protein and lipid: Effect on physiological responses of Labeo rohita

A 60- day feeding trial was conducted to study the effects of feeding de-oiled rice bran (DORB) with different dietary protein and lipid levels on the haematological parameters along with digestive, oxidative stress and metabolic enzyme activities of Labeo rohita fingerlings. Nine semi-purified isocaloric (383 Kcal DE/100 g) diets containing varying level of protein (26, 28 & 30%) and lipid (6, 7 & 8%) were formulated as P30L6, P30L7, P30L8, P28L6, P28L7, P28L8, P26L6, P26L7 and P26L8 (P-Protein, L-Lipid), respectively. The fish fed diet with the lowest protein with the highest lipid (P26L8) exhibited significantly (p < 0.05) higher intestinal amylase and lipase activity but no significant variation were observed in total protease activity. The higher HSI (Hepatosomatic index) and ISI (Intestinal somatic index) value along with lower SOD (Superoxide dismutase), CAT (Catalase) and GST (Glutathione-s-transferase) activity of liver and gill were also observed in the same group (p < 0.05). The highest protein and lowest lipid (P30L6) fed group showed significantly (p < 0.05) higher LDH (Lactate dehydrogenase) activity in liver and muscle tissue of Labeo rohita, whereas, there is no significant variation was observed in MDH (Malate dehydrogenase) activity. The haematological parameters like serum protein, albumin, globulin and glucose contents were also significantly (p < 0.05) higher in P26L8 group. RBC (Red blood cell), Hb (Haemoglobin), WBC (White blood cell) and NBT (Nitroblue tetrazolium) value were significantly affected by the dietary lipid level. Fish fed P26L8 treatment group had significantly (P < 0.05) higher AST (Aspartate amino transferase) and ALT (Alanine amino transferase) activity in liver and muscle tissues. Based on the results, it is concluded that feeding de-oiled rice bran with 26% dietary protein and 7% or 8% lipid to L. rohita have no adverse effect on haematological and serum biochemical parameters.

Effect of Different Dietary Protein and Lipid Levels on the Growth, Body Composition, and Intestinal Digestive Enzyme Activities of Juvenile Yellow Drum Nibea albiflora (Richardson)

An 8-week feeding trial was conducted to determine the optimal dietary protein-to-lipid ratio for juvenile Nibea albiflora with an initial weight of (11.76 ± 0.20) g. Nine experimental diets containing different concentrations of protein (40%, 47%, or 54%) and lipids (5%, 9%, or 13%) in a 3 × 3 factorial experimental design were tested in triplicate groups of fish, while the protein-to-energy (P/E) ratios of the diets varied in the range of 19.74–28.32 mg kJ−1. Results showed that fish fed diets containing 9% or 13% lipids with 54% protein exhibited significantly higher weight gains and specific growth rates than those fed other diets. The feed conversion rate of fish fed the diet with 40% protein and 5% lipids was significantly poorer than that of fish fed other diets. The protein efficiency rate of fish fed diets with 5% lipids was significantly lower than that of fish fed 9% or 13% lipid diets. Carcass lipid and energy contents were positively correlated with dietary lipid level regardless of protein level. Fish fed a 54% protein diet showed the highest trypsin activity. The intestinal lipase activity of fish fed the diet containing 13% lipids was significantly higher than that of fish fed 5% or 9% lipid diets. These results demonstrate the high protein dietary requirements of N. albiflora. A diet containing 54% protein and 9%–13% lipids with a P/E ratio of 26.2–27.81 mg protein kJ−1 can be considered optimal for juvenile N. albiflora.

A moderately high level of dietary lipid inhibited the protein secretion function of liver in juvenile tiger puffer Takifugu rubripes

Tiger puffer have a unique lipid storage pattern. They store lipid predominantly in liver. To investigate the hepatic physiology of tiger puffer in response to a moderately high level of dietary lipid, a 74-day feeding trial was conducted, followed by a hepatic transcriptome assay. Two experimental diets which had an optimal (10.44%, Control) or moderately higher (14.64%, high-lipid diet, HL) dietary lipid level was formulated. Each diet was fed to triplicate tanks. No significant difference was observed in growth and feed efficiency between the two groups, but the survival was significantly lower in group HL. The HL diet also resulted in significantly higher lipid accumulation in liver, which was reflected in the hepatic histology. The biochemical parameters in serum confirmed the existence of stress in liver caused by high lipid intake. A total of 63 differentially expressed genes between groups were observed in the hepatic transcriptome assay, which were primarily enriched in Gene Ontology (GO) terms such as Endopeptidase activity, Secretion, and Organic acid transport, as well as in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways such as Protein processing in endoplasmic reticulum and DNA replication. The HL diet tended to inhibit the protein synthesis and secretion in liver, and this was evidenced by activities/concentrations of selected proteins secreted into intestine. Genes related to liver protection and repair were transcriptionally stimulated by diet HL. In conclusion, compared to the optimal lipid requirement, a moderately higher lipid level in the diet for tiger puffer did not compromise the growth performance, but tended to inhibit the protein secretion function of liver and stimulate the processes related to liver protection and repair. The present results will be beneficial to both feed management in tiger puffer farming and elucidation of lipid metabolism characteristics in fish which store lipid in liver.

Effect of dietary lipid content and stocking density on digestive enzymes profile and intestinal histology of rainbow trout (Oncorhynchus mykiss)

The effect of both dietary lipid level and stocking density on digestive function was tested in young rainbow trout under culture conditions. Two dietary lipid levels (14 and 33%) and three culture densities (15, 30 and 40 kg/m3) were assayed in triplicate lots: L14/D15, L14/D30, L14/D40, L33/D15, L33/D30 and L33/D40. Intestinal activities of amylase, lipase, trypsin, chymotrypsin, total protease (at different pHs) as well as some biometric parameters such hepatosomatic index (HSI) and digestivesomatic index (DSI) as indicative of perivisceral fat accumulation, were determined after a 12-weeks experimental period. A histological study of intestine was carried on to evaluate changes in tissue architecture. Fish fed on higher lipid diets grew more and accumulated a higher amount of fat in perivisceral tissue, although higher stocking density reduced this trend. According to digestive capacity, higher lipid intake induced an activation of lipase activity that was not apparent when fish were held under the highest rearing density. By other hand, dietary lipids promoted a significant inhibition of protease activity in fish under high density conditions. These results seem to indicate a clear interaction between both variables. In this study, it was manifested a general effect of dietary lipids level and culture density on digestive profile. These interactions should be taken into account when foreseeing the digestive utilization of a commercial feed at different culture conditions to improve fish production.

Effects of different dietary lipids concentrations on the egg production and egg quality produced by Macrobrachium acanthurus females

The sexual maturation and reproduction of crustaceans are very demanding processes for energy and nutrients. Females require the nutrients to deposit them into the eggs and allow the healthy development of embryos and early larvae survival. The lipids are essential nutrients related to the sexual maturation and the egg production, as they are sources of metabolic energy for the gonad development, as well structural molecules for the embryonic tissue formation. This work presents the effects of different dietary lipid levels (10, 12.5, 15, 17.5 and 20% of a mixture of krill and cod liver oil as lipid sources), on the growth, egg production, and egg quality, of freshwater prawn Macrobrachium acanthurus females fed during 60 days. The results showed that an inclusion higher than 15% of lipids, improved the egg production and the content of protein and lipids significantly. A lipid inclusion between 15 and 17.5% might be optimal for maturation and egg production of the females of M. acanthurus .

Growth performance, feed efficiency and whole-body chemical composition of the oriental river prawn, Macrobrachium nipponense, fed different dietary protein and lipid levels

A 56 days grow-out experiment with three protein levels (35, 40 and 45%) and three lipid levels (5, 10 and 15%) was conducted to evaluate the optimum protein and lipid ratio for Oriental River Prawn (Macrobrachium nipponense). Four hundred and five prawns, with mean (± SD) weight of 1.40 ± 0.04 g were distributed in 27 glass aquaria and were fed four times daily. Results showed that interaction between protein and lipid was significantly affected on all of the growth indices (P 0.05). The results of this study showed that Oriental River Prawn represents the best performance at level of 45% protein and 5% lipid.

Molecular characterization of microtubule-associated protein 1-light chain 3B in Megalobrama amblycephala fed with high fat/berberine diets.

This study tested the effect of berberine on autophagy-related protein of Megalobrama amblycephala fed with high fat diet under different feeding modes. The full-length complementary DNA (cDNA) of microtubule-associated protein 1-light chain 3B (LC3B) was 1871bp with an open reading frame of 378bp encoding 125 amino acids. High homology at nucleotide and amino acid sequences to carp LC3B was revealed though sequence analysis. LC3B was mainly (P <0.05) expressed in hepatopancreas but lower in several peripheral tissues, including gill, intestine, kidney, and spleen. The fish (average initial weight 4.70 ± 0.02g) were fed with eight experiment diets containing two lipid levels (5 and 10%) or four berberine-feeding modes (without berberine, supplementing 50mg/kg berberine at 2-week intervals, 4-week intervals, or continuous) for 8weeks. The results showed that the numbers of autophagosomes and hepatopancreas LC3B messenger RNA (mRNA) expression levels were significantly (P <0.05) affected both by dietary lipid level and beberine feeding mode, and the highest (P < 0.05) numbers of autophagosomes and LC3B expression levels were observed in fish at berberine continuous feeding mode groups. The findings may provide the molecular mechanisms underlying lipid metabolism and immune effect of berberine, which was associated with enhanced autophagy in fish.

Effect of dietary lipid levels on growth performance, fatty acid profile and enzymatic activity of juvenile swimming crab,Portunus trituberculatus

The main objective of this investigation was to study the lipid requirements of the early juvenile (C1) swimming crab (Portunus trituberculatus) based on growth performance, survival, moulting and fatty acid profile. Four test diets were formulated with graded lipid levels (3.63%, 6.70%, 10.72% and 13.91%). Each diet was fed to 4 replicates of crabs (30 crabs per replicate initial weight (8.4 ± 0.1 mg). In this study, crabs fed diets with 13.91% lipid had significantly (p < 0.05) higher survival than crabs fed with 3.63% lipid, but no significant (p > 0.05) improvement of survival was observed when dietary lipid increase from 6.70% to 13.91%. Crabs fed diets with 10.72% and 13.91% lipid had significant higher weight gain(WG) than crabs fed with 3.63% lipid. While crabs fed with diets containing 6.70%, 10.72% and 13.91% lipid showed no significant (p > 0.05) difference in weight gain(WG). Moreover, the lowest moulting number was observed in crabs fed diets with 3.63% lipid, but there was no significant difference (p > 0.05) among other groups. The content of LC-PUFA and DHA in the crabs fed diets with 3.63% lipid was significant (p < 0.05) lower compared to other groups. But there was no significant (p > 0.05) difference in EPA and ARA content among all groups. The activity of lipase increased as dietary lipid level increased (from 6.70% to 10.72%). However, beyond 10.72%, a significant (p < 0.05) decreased in lipase activity was observed. The regression analysis of weight gain data indicated that crab fed diet containing 10.47% lipid level is considered as optimum lipid level for its maximum growth and moulting process.

Dietary Cholesterol, Lipid Levels, and Cardiovascular Risk among Adults with Diabetes or Impaired Fasting Glucose in the Framingham Offspring Study.

Previous recommendations to limit dietary cholesterol intake have been eliminated for most adults. Questions remain about whether dietary cholesterol has adverse cardiovascular effects among individuals with impaired fasting glucose or diabetes (IFG/T2DM). We used data for 993 adults (40.9% female), ages 35–<65 years, with prevalent IFG/T2DM in the prospective Framingham Offspring Study to address this question. Dietary cholesterol was assessed using 3-day diet records at exams 3 and 5 and used to classify subjects into sex-specific tertiles of mean cholesterol intake. Outcomes included fasting lipid levels over 20 years and incident cardiovascular disease (CVD). Statistical analyses included repeated measures mixed regression models and Cox proportional hazards models to adjust for confounding. Among adults with T2DM/IFG, there was no consistent association between dietary cholesterol intake and fasting low-density lipoprotein (LDL), high-density lipoprotein (HDL), LDL/HDL ratio, or triglycerides over 20 years of follow-up. In longitudinal analyses, the adjusted hazard ratio for CVD in the highest (vs. lowest) sex-specific tertile of cholesterol intake was 0.61 (95% CI: 0.41, 0.90). These analyses provide no evidence of an adverse association between dietary cholesterol and serum lipid levels or atherosclerotic CVD risk among adults with prevalent IFG/T2DM.

Effects of dietary lipid and protein levels on growth and physiological metabolism of Pelteobagrus fulvidraco larvae under recirculating aquaculture system (RAS)

A feeding trial was conducted to investigate the effects of different dietary lipid and protein levels on both the physiological metabolism and the anti-oxidation of Pelteobagrus fulvidraco larvae cultured in recirculating aquaculture system (RAS). In the present study, four test diets (P52L13, P52L9, P48L13, P48L9) were formulated by two different lipid levels (13%, 9%) and two different protein levels (52% and 48%) in a factorial manner (2 × 2) to provide four different dietary protein-lipid ratios (P:L) 3.95, 5.71, 3.56 and 5.46. Each treatment was assigned in triplicate. Two days after hatching, larvae were fed with Artemia sp. for 1 day, and then were co-fed the Artemia sp.plus the tested diets for 2 days, finally fed test diets for 18 days. The results were in keeping with that of growth performance, showed that the larvae fed on P52L13 and P48L9 diets had significantly higher activities of lipoprotein lipase (LPL), glutamic-pyruvic transaminase (GPT), superoxide dismutase (SOD) and catalase (CAT) than other two groups (P < 0.05). The highest activities of lysozyme (LZM) and glutathione (GSH) were observed in group P52L13 and P48L9, respectively (P < 0.05). Concerning dietary lipid levels, the highest activities of LPL, GOT, SOD, CAT and LZM were observed for larvae fed diets containing 13% lipid (P < 0.05). Regarding to antioxidative factors, same trend was observed for larvae fed diets with 52% protein (P < 0.05). Our results clearly suggested that P52L13 and P48L9 diets could promote the metabolism of protein and lipid, and antioxidative ability of P. fulvidraco larvae in RAS, meanwhile, P52L13 diet is the superior.

Optimal dietary lipid level promoted ovary development of Chinese sturgeon (Acipenser sinensis) broodstocks

A one-year feeding trial was conducted to determine the effects of dietary lipid level on gonad development and steroidogenesis-related gene expressions of Chinese sturgeon (Acipenser sinensis). Three isonitrogenous experimental diets (L10, L14 and L18) were compounded with different lipid levels. Results of the feeding trial showed that 2 female Chinese sturgeons in L18 group had developed the ovary to stage III. Chi-square independence test indicated that ovary development was significantly affected by dietary lipid level (P < .05). Po and d values of ovary also increased with dietary lipid level. Serum estradiol (E2) and testosterone (T) of L14 group was significantly higher than those in the other two groups (P < .05). Blood urea nitrogen (BUN) content decreased as dietary lipid level increased, while triglyceride (TG) and glucose (GLU) contents increased with dietary lipid level (P < .05). Vitellogenin receptor (vtgr) mRNA expression increased with dietary lipid level (P < .05); Gene expressions of androgen receptor (ar), cytochrome p450 17A1 (cyp17a1), steroidogenic acute regulatory protein (star), follicle stimulating hormone receptor (fshr), luteinizing hormone receptor (lhr) and cytochrome p450 aromatase (cyp19a1) were significantly higher in L14 group than in other groups (P < .05), whereas mRNA expression of leptin receptor (lepr) and DNA-binding protein inhibitor ID-1 (dbi) in L14 group were significantly lower (P < .05). Based on the gonad development, higher dietary lipid level (16.31%) would promote ovary development of Chinese sturgeon broodstocks through the elevation of vtgr expression to increase the assimilation of vitellogenin in ovary.

Feeding de-oiled rice bran (DORB) to Rohu, Labeo rohita: Effect of varying dietary protein and lipid level on growth, body composition, and insulin like growth factor (IGF) expression

A 60-day feeding trial was conducted to optimize the dietary protein (30, 28 & 26%) and lipid (6,7 & 8%) levels for optimum inclusion of 33% de-oiled rice bran based (DORB) diets on the growth performance, feed utilization, expression of insulin like growth factor (IGF-I and IGF-II) and RNA/DNA ratio in the Labeo rohita. The formulated diets were different combination of protein and lipid levels while fixing the level of DORB at 33% viz., P30L6, P30L7, P30L8, P28L6, P28L7, P28L8, P26L6, P26L7 and P26L8 (P-Protein, L-Lipid), respectively.Two hundred seventy fingerlings (average wt. 5.56 g ± 0.2) were equally distributed in nine treatments in triplicates with 10 fish per tank. The weight gain % (WG) and specific growth rate (SGR) increased with the decreasing protein level and increasing lipid level in diets. Highest weight gain % and specific growth rate was along with lowest FCR were recorded in the group fed with 26% protein and 7% lipid. The protein efficiency ratio (PER) was significantly (p < 0.05) higher in P26L7 and P26L8 groups. The expression of IGF-I mRNA was found to be higher in P26L7 group as compared to other groups. Though the expression of IGF-II was significantly (p < 0.05) higher in P26L7 group, it was similar to the P26L8 group. The RNA concentration and RNA/DNA ratio was found significantly (p < 0.05) higher in the P26L7 group. Dietary protein level did not affect significantly (p > 0.05) on whole body protein and lipid content. Significantly (p < 0.05) higher body lipid level and lower protein level was found at 26% protein and 8% dietary lipid fed group. Hence, diet containing 33% DORB with 26% crude protein and 7% lipid level is optimal for supporting maximum growth and feed utilization of Labeo rohita.

Dietary lipid levels could improve growth and intestinal microbiota of juvenile swimming crab, Portunus trituberculatus

An 8 week feeding trial was conducted to evaluate the effects of dietary lipid levels on growth and intestinal microbiota of juvenile swimming crab. Three isonitrogenous (47% crude protein) diets were formulated to contain 5.8%, 9.9% and 15.1% crude lipid levels, respectively. Three groups of swimming crab (n = 60 per group) were randomly assigned to each diet. An Illumina-based sequencing method was used to analyze the intestinal bacterial composition of the crabs. The results indicated that swimming crab fed the diets containing 5.8% and 9.9% lipid had significantly higher weight gain and survival than those fed the 15.1% lipid diet. Proteobacteria, Fusobacteria and Tenericutes were dominant in the intestines of swimming crab regardless of the diet; the relative abundance of Fusobacteria decreased while Proteobacteria increased with increase of dietary lipid levels. Swimming crab fed the diets containing 9.9% and 15.1% lipid had a higher abundance of pathogenic bacteria than those fed the 5.8% lipid diet. These results indicate that dietary lipid levels could affect the composition of the intestinal microbiota; also, higher dietary lipid levels have a negative impact and increase the potential risk of disease in swimming crab.

Changes of visceral properties and digestive enzymes in the herbivorous marine teleost Siganus canaliculatus fed on different diets

The rabbitfish Siganus canaliculatus is one of the few cultured herbivorous marine teleosts. To better understand the digestive physiology of this fish and provide data for designing formulated feed using macroalgae as an ingredient, the changes of visceral properties and digestive enzyme activities were investigated after the juveniles were fed on different types of food including raw fish (RF), formulated diet (FD) or macroalgae Enteromorpha prolifra (EP) and Gracilaria lemaneiformis (GL) for eight weeks. The results showed that the hepatosomatic and viscerosomatic indices in the RF and FD groups, as well as the relative intestine length (RIL) in the EP and GL groups, were significantly higher than those in other groups. Additionally, differences in the histological structure of the liver and anterior intestine were also observed among different dietary groups. The hepatic nuclei were displaced to the periphery by lipid inclusions in fish fed RF. The highest levels of mucosal folds were found in the anterior intestines of fish fed macroalgae. Digestive enzyme activity profiles showed obvious fluctuations in the first three weeks, and then leveled off in the following weeks. The levels of protease, lipase and α-amylase in the alimentary tract showed changes related to the levels of dietary protein, lipid and carbohydrate, respectively. Although macroalgae significantly inhibited the activity of protease in the stomach, it increased RIL and the number of mucosal folds in the anterior intestine so as to compensate for the influences on protease activities in the stomach. This study suggests that the digestive tract of rabbitfish can well adapt to different diets, and needs about three weeks to physiologically acclimatize to the nutritional status, thus implying that rabbitfish are somewhat omnivorous.

Optimal Dietary Protein and Lipid Levels for Juvenile Yellowstripe Goby (Mugilogobius Chulae), a Proposed Laboratory Fish

Mugilogobius chulae is a small euryhaline or estuarine goby recently proposed as an ideal species for use in ocean environmental toxicology studies. However, the nutritional requirements of M. chulae remain unknown. Eight experimental diets at one of four protein levels (35%, 40%, 45%, or 50%) and two lipid levels (5% or 10%) were formulated to investigate the effects of differing dietary protein and lipid levels on the growth performance, body composition and liver morphological condition of M. chulae. Juvenile gobies (1760 individuals, 0.011±0.001 g fish-1) were randomly allotted to 32 tanks (four replicates of each of the eight treatments) and fed twice a day for 9 weeks. Weight gain (WG) and specific growth rate (SGR) increased significantly with increasing dietary protein from 35% to 45% (P 0.05). Whole-body crude lipid and linoleic acid (C18:2n-6) contents in juvenile M. chulae increased significantly with increasing dietary lipid content (P 0.05), and no pathological changes were observed in the liver, lipase activity significantly decreased (P < 0.05). The dietary protein level driving optimal WG and SGR also led to the highest trypsase activity. Thus, 45% crude protein and 5% lipidis sufficient to ensure good growth performance in juvenile M. chulae, and this diet appears to have no substantial adverse effects.